A protein fraction isolated from defatted watermelon seed (Citrullus lanatus) flour with 1.0 M NaCl was evaluated for its functional properties. The water retention capacity of the isolate (320 ml/100 g) was found to be similar to cottonseed protein isolate. The fat absorption capacity was 190 ml/100 g. The alkaline pH 11.3 gave the highest foam (89%) with optimum stability around the neutral pH 7. The emulsification capacity was highest at the acidic pH 2.2. Sodium chloride molarity affected foaming and emulsifying properties. Other functionalities such as formation of gels, wettability and bulk density are also reported. Watermelon seed protein isolate can be considered of great potential for incorporation into human food products not only as a dietary protein supplement but also a functional agent in different food systems.